The present invention relates to methods and apparatus for separating, feeding and/or folding sheets. The invention is particularly useful for separating and feeding sheets of fabric from a stack or pile of fabric sheets according to the method and apparatus described in U.S. Pat. No. 4,635,917 now U.S. Pat. No. 4,635,917, assigned to the same assignee as the present application, and is therefore described below with respect to this application, but it will be appreciated that the invention could advantageously be used in other applications as well, such as for folding fabrics and other similar sheet material.
The above-cited U.S. Pat. No. 4,635,917 describes a method and apparatus for feeding sheets from a stack particularly useful with respect to fabrics or other limp or porous materials. Feeding such materials has heretofore presented considerable difficulty, as compared to the feeding of paper, cardboard, or similar sheets which is relatively simple. Briefly, the method and apparatus described in the above-cited patent application comprises an arrangement for: engaging the opposite edges of the upper sheet of the stack by a pair of restrainer members; bringing a pick-up head into engagement with the upper sheet of the stack while producing air streams from the pick-up head directed outwardly across the opposite edges of the upper sheet of the stack; lowering the pick-up head to depress the stack below the restrainer members whereby the air streams cause the opposite edges of the upper sheet of the stack to curl upwardly to clear the restrainer members; lifting the upper sheet from the stack; and permitting the stack to rise so as to bring the next sheet into engagement with the restrainer members, whereupon the stack is ready for feeding the next upper sheet.
Such an arrangement has been found to be far more effective than the previously known arrangements for feeding fabrics and other similar types of limp or porous materials. However, difficulties have been observed with respect to special types of fabrics having a multitude of free fibers or threads projecting from their faces, which fibers or threads tend to intermesh and become entangled with the fibers and threads of the adjoining layers, thereby making their separation extremely difficult and/or requiring extremely high air flow rates.